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arXiv · 0803.3306

Fourfold degenerate columnar-dimer ground state in square lattice antiferromagnets

Rakesh Kumar·Brijesh Kumar
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Abstract

We construct and study two frustrated quantum spin-1/2 models on square lattice, which are like the antiferromagnetic $J_1$-$J_2$ model with some additional four-spin exchange interactions. These models admit an exactly solvable case in which the ground state consists of four degenerate columnar-dimer singlet (CDS) configurations. Away from the exact case, we employ bond-operator mean-field theory to investigate the evolution of the ground state by varying the interaction parameters. The mean-field calculation reveals a quantum phase diagram in which the CDS phase undergoes a continuous phase transition to either Néel or collinear ordered antiferromagnetic phases.

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Rakesh Kumar, Brijesh Kumar. 2008-03-23. Fourfold degenerate columnar-dimer ground state in square lattice antiferromagnets. https://doi.org/10.1103/physrevb.77.144413

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